In image transfer photography processing liquid is released into contact with one or more imagewise exposed radiation-sensitive imaging layers located on a photographic support. The imaging layers are capable of providing mobile image-forming material during processing in a pattern which is a direct or inverse function of imagewise exposure. A receiving layer is located adjacent the imaging layers during processing to receive the image-forming material and to form a viewable transferred image.
(a) The Problem Addressed by the Invention PA0 (b) Specific Prior Art Relevant to the Problem or Most Nearly Analgous to the Inventive Structure
In the most common image transfer film unit constructions it is desirable to provide a thin, uniform layer of processing liquid over at least the entire area of the image transfer film unit in which a viewable image is intended to be formed. Nonuniformities in the processing liquid often translate into nonuniformities in the transferred image.
A further complication is introduced by further requiring that the image transfer film unit have the capability of being handled during processing. This requires the processing liquid to be entirely contained within the film unit. Thus, in most instances image transfer film units capable of being handled during processing include both a support and a cover sheet that are impervious to processing liquid.
In integral image transfer film units the processing liquid is sealed within the unit before, during, and after processing. Most commonly, the processing liquid is initially contained in a reservoir or pod laterally displaced from the area of the unit intended to form a viewable image. After imagewise exposure of the unit the processing liquid is released from the pod by passing the unit between pressure rollers intended to spread the processing liquid uniformly within the viewable image-forming area of the element. Both a cover sheet and a support are required to confine and laterally direct the processing liquid. Both the cover sheet and the materials forming the pod increase the film unit's bulk, which some users find unattractive.
Land U.S. Pat. No. 3,069,266 teaches mounting a support having a silver halide emulsion layer coated thereon in proximity to a support having a receiving layer thereon to form a capillary interspace therebetween. Upon release of processing liquid from a laterally displaced reservoir or pod the processing liquid is drawn by capillary action into the interspace and thereby distributed between the emulsion and receiving layers. Columbus U.S. Pat. Nos. 4,233,029 and 4,271,119 provide additional illustrations of transporting liquid by capillary action.
Liang U.S. Pat. No. 3,784,382 discloses an image transfer film unit having an internal support. Specifically, Liang discloses interposing a porous polymeric support having a porosity between about 1 and 25 percent between silver halide emulsion layers and a dye imaging receiving layer. Liang states, "Since the image-forming dyes travel through the porous support which contains straight-through pores, the dyes reach the dye image-receiving layer with a minimum of lateral diffusion, thereby producing an image having greater sharpness."
Whitmore U.K. patent application No. 2,042,753A discloses image transfer film units in which radiation-sensitive silver halide can be located in closed-end microcells embossed or otherwise formed in the photographic support. Additionally or alternatively an image receiving material, such as a mordant, can be positioned in closed-end microcells embossed or otherwise formed in a cover sheet. Processing liquid is introduced between the support and cover sheet in a conventional manner.
Jaskowsky Defensive Publication T880011 discloses an imaging element wherein a layer containing an imaging dye or pigment in pores extending between its major surfaces is mounted so that each pore at one terminus lies adjacent a deformable resin layer which in turn lies adjacent a diazo blowing agent. Each pore at its remaining terminus contacts a semi-permeable membrane which in turn overlies a receiving manner. When the diazo blowing agent is exposed to light, gas is explosively generated causing the deformable resin layer to impinge on the porous layer containing dye or pigment. This in turn forces dye or pigment from the pores in this area, and the dye or pigment traverses the semi-permeable membrane to form a viewable image in the receiving member.